Improvement in valve-gears for engines



UNITED STATE rer..

LEONARD ATWOOD, OF NEW YORK, N. Y., ASSIGNOR TO P. H. WALKER, OF BOSTON,MASSACHUSETTS.

IMPROVEMENT IN VALVE-SEARS FOR ENGINES.

Speciiication forming part 0f Letters Patent No. 117,141, dated July'lS, 1871.

To all whom it may concern:

Be it known that I, LEONARD ATwooD, of the city and State of New York,have invented an Improvement in Valve-Gear for Engines; and

. the following is declared to be a correct description ofthe same.

This invention is designed for cutting oft' the supply of steam at anydesired point by a movement derived from the governor. 1 make use ofmovable cut-off plates connected by links with cranks on opposite sidesof a shaft that is turned by a connection to the governor or otherwise,so as to cover, by said plates, the inlet-ports to a greater or lesserextent, according to the speed of the engine. The main valves, slidingbetween these cut-off plates andthe valve-seat, do not tend to revolvethe shaft, because the arrangement of the cranks and links is such thatthe action is balanced, the friction upon one plate tending to move theshaft in one direction, and the friction on the other acting in theopposite direction, and, being equal, they balance; hence the governorcan move the cut-off plates with ease.

l In the drawing, a represents the cylinder, in which is a piston, a',and b is the valve-seat. c

` is the main valve, moved by the rod d, and r is the secondary orcut-oli valve upon the valve c, and moved by the rod s. These parts areof any usual size an d proportion, and the ports are made in any usualway and do not need further description. The valve 1 is made with theinletI ports through it, so that a seat will be provided upon its uppersurface for the cut-o plates i and l, and'these are connected, by thelinks j' and g, to the cranks IL and a upon the shaft o that passesthrough the steam-chest at right angles to the valve r, and to thisshaft o a connection is made to a governor or other device for changingthe position of the cut-oit' plates t' l, so as to thereby regulate thespeed ofthe engine. It will be apparent that the movement of the valve rbetween the cut-oft' plates and the valve c willv not tend to move theshaft o, because while the friction on one of the plates tends to movethe shaft o in one direction the iriction on the other tends to move itin the other direction, hence the one balances the other, and the partscan be moved with great ease by the governor or by hand, and in thatposition the shaft o will remain until again moved by the governor or byhand. The edges of these cut-oft' plates, closing the ports through thevalve 'r more or less quickly, according to the positions of suchplates, cut oit' the steam at whatever portion ofthe stroke may bedesired.

I am aware that cut-oli" plates operated by cams have been employedbetween the valve and sea-t; but in this construction the friction uponthe cut-olil plates is much greater than in my improvenient, andthelinks and cranks l employ move with much less friction than the saidcams, hence can be easily operated by the governor.

I claim as my invention- A pair of cut-off plates on the upper surfaceof the valve connected to cranks on the opposite sides of a shaft thatis turned to control the cutott action of such plates, substantially asset forth.

Signed by me this 13th day of February, A. D. 1871. I

LEONARD ATVVOOD.

Vitnesses:

Unas. H. SMITH, Gno. T. PINCKNE Y.

